OBJECTIVETo investigate apoptosis-inducing effect and its mechanisms of HY-1, a carbazole alkaloid, on human erythroleukemia K562 cells.

METHODSCell proliferation was detected by sulforhodamine B (SRB) assay after treated with HY-1 at indicated doses. Cell cycle analysis was performed by flow cytometry, mitochondria membrane voltage change was assessed by rhodamine 123 staining, annexin V-PI apoptosis detecting kit and DNA agarose gel electrophoresis were used to identify apoptosis-inducing effect of HY-1. The alterations of apoptosis-relating proteins were detected by Western blot.

RESULTSThe IC(50) of HY-1 in K562 cells was (29.05 +/- 0.90) micromol/L by SRB assay. HY-1 had significant apoptotic inducing effect on K562 cells in a dose- and time-dependent manner as verified by appearance of Sub-G(1) peak on histogram of flow cytometry analysis, reduction of mitochondria membrane voltage, appearance of double positive cell group in Annexin V-PI apoptosis detecting test, and remarkable DNA ladder. The expression of cytosolic cytochrome c was apparently increased. Pro-caspase-9, pro-caspase-3 and PARP were all cleaved to active segments. There was no change in the expression of caspase-8.

CONCLUSIONHY-1 exerts its anticancer activity through triggering apoptosis of K562 cells by mitochondria-activating pathways.